For making prints of negatives or slides it is now common practice to use a tape of sequential negatives or slides in order to obtain higher speed in printing centers, since these tapes can be practically automatically fed to an exposing machine (printer), in which all necessary processes for making prints are performed. These processes comprise inter alia the application of a code number, the assessment of the correct side to be facing the source of light, the assessment of the coverage and the colour value of the negative or positive and the control of the printing part proper with the associated light source and filters, if any, via a memory, as the case may be.
In making prints of negatives it is common practice to start by a roll film, which is passed either as a whole or in parts, for example, strips of 4 to 6 negatives, through the printing machine (printer). Since these film strips have a given amount of rigidity, it is possible to transport them as such through the printer. However, in particular in the case of miniatures one side of the negative film or part thereof is sometimes enclosed between strips and stuck thereto. These strips are then moved by a transport mechanism through the printer.
In the case of slides the question is usually quite different. Up to recent years first a so-called intermediate negative had to be made for making a print of a slide. This intermediate negative was then processed in a printing machine in quite the same manner as a normal negative. At present it is, however, possible to make a print on photographic paper directly from slides. This has offered to each client the possibility of having made a print at low price. Making an intermediate negative, as originally required, materially increases, of course, the costs of the whole process. Since a client is, in the first place, interested in slides for projection and wants a print of only a very limited number, the client usually hands framed slides to the photographer. These framed slides, hereinafter also termed frames, could be individually processes in a printing machine, since they are rigid. However, such a process would be very time-consuming. Therefore tapes, for example, of synthetic material, have been developed, which comprise a large number of sequential, relatively separated compartments in which the slide frames can be placed. Such a tape consists, in principle, of two ladder-shaped parts fastened to one another at the areas of the rungs of the ladder. The parts between the "rungs" have approximately the dimensions of a slide frame and have openings for the picture part of the slides, that is to say, the part carrying the image information. If the tape is made from synthetic material, the "rungs" of the ladders are interconnected, for example, by high-frequency welding. However, adhesives may also be used. Although the use of such tapes, when frames are placed in the compartments, allows a very high rate of the printing process proper, the great disadvantage is that the slide frames have to be slipped into the compartments. In many cases this done by hand, although it is possible to apply some mechanisation, for example, by opening the compartments by means of an air stream and by slipping the frame mechanically into the compartments. This processing step is still time-consuming.
The use of a tape of interconnected compartments as described above provides apart from the possibility of a higher rate of processing in the printer proper, the advantage that the tape can be wound or folded for transport purposes. In some cases the photographer may supply tapes to the printing center in which slide frames have already been slipped.
The tape is automatically transported in the printer. It is then necessary for each slide frame to be exactly positioned in the printer proper for making a print. In some printers this is performed with the aid of a light beam and a photo-electric cell capturing said beam after the beam has passed through the "rungs" of the tape. In this part of the tape, which is double, considerable loss of light and dispersion of the light occur. Therefore it is necessary to use an accurately directed, concentrated light beam, which requires an expensive optical system. This could be improved by providing a small aperture in the "rungs" for passing the light beam. However, this requires additional processing and it is, therefore, less recommended.
A further disadvantage of the use of such tapes is that each compartment has to be slightly larger than the dimensions of a frame, since otherwise insertion of the frames becomes even more difficult. Then, however, the place of a slide frame in a compartment is not fully fixed. This may give rise on the one hand to transport difficulties and on the other hand to prints not fully corresponding to the picture information of the slide.
A further disadvantage of the use of the known tapes is that the tapes are usually made from synthetic material and can, therefore, be only provided with indications, for example, code numbers with the aid of special felt pens. Moreover, the tapes of the kind described above are relatively expensive.